Luminescent properties of Eu3+-activated lithium rare earth borates and oxyborates

The luminescence characteristics of Eu3+ in the borates Li6Y(BO3)(3) and Li3La2(BO3)(3) and the recently discovered oxyborates LiLa2O2BO3, LiLn(6)O(5)(BO3)(3) (Ln=Y,Gd) and Li2Lu5O4(BO3)(3) have been investigated and compared to those in the borates LnBO(3) (Ln = La,Y) and the oxyborates "Ln(3)BO(6)" (Ln = La,Gd). The probability of electric dipole f-f transitions is generally markedly higher in oxyborates than in borates. This is ascribed to the highly, anisotropic environment of rare earth ions and the low position of the charge transfer states. Consequently, the Eu3+ -activated oxyborates are characterized by a deeper red emission and faster decay. (C) 2002 Elsevier Science B.V. All rights reserved.